A wrist-held device for the independent and on-line surveillance of movement and physical condition is not yet available. Traditionally, the surveillance of patient movement out of a region has been effected by using extra-personal sensors, e.g. by monitoring the use of a door. The problems include a long monitoring time, high installation costs as well as false alarms as a person under surveillance leaves the space without switching off the surveillance. There are also portable radio transmitters provided with a switch for indicating the posture of a person. A problem with such devices are false alarms as the user must remember to take off the device when lying down. Another problem is that some surveillance is only active when a person is on his or her feet.
Prior monitoring devices are capable of monitoring the heart, however such devices do not provide information about motoric activity and are not suitable for personal motion control or surveillance. The heart monitoring devices are also traditionally expensive and require frequent battery replacement. Such devices are also not suitable for applications with many users in a restricted area or when long-term surveillance is required.